Night Surveillance - White Light Illuminator Test

By: Benros Emata, Published on Jul 17, 2011

Getting quality surveillance images at night can be quite a challenge. A number of techniques, with widely varying price points and tradeoffs, are possible. In this report, we share our test findings on the newest emerging trend in night time surveillance - adding white light LED illuminators.

Background

Almost all surveillance cameras have natural performance limits when it gets really dark out. Even the 'best' cameras will struggle needing to pump up the gain while overall image details rendered diminish. One common option with megapixel cameras is slowing the shutter but this increases the risk of creating ghost like images of moving objects.

Since there is only so much that can be done with conventional surveillance cameras, three common steps are generally employed to improve night time performance:

Add street lighting: This can work very well but also requires an expensive construction project. This is easy to do with new construction but generally hard otherwise.

Use thermal imagers: Thermal cameras do not need visible light at all and can 'see' objects far away. The downside is the cameras are expensive ($3,000 to $30,000) and provide minimal details. As such, these tend to be primarily used in critical infrastructure projects.

Use IR illuminators: This is, by far, the most common step to improve night time surveillance. IR light, visible to many security cameras but not the human eye, can be used to provide significantly improved night time image. The main downside is that it does not work for color cameras or color capture mode.

Using white light LEDs illuminators is a fourth way to improve night time image quality. Like street lighting, white light LED illuminators add visible light. However, white light LED illuminators are much smaller than street lamps and can easily be installed adjacent to security cameras. Here's what the illuminators look like relative to the size of a hand:

These illuminators can be used to provide spot illumination on specific areas where surveillance is desired. They allow for color imaging and add the natural deterrent of visible light.

We setup the two illuminators in a dark open field, and took lux readings at various distances and locations, comparing the light levels with just ambient light (i.e. dark, under 1 lux) and with the illuminators on. The results were documented in 2 visual maps (one for each illuminator). Below is a preview of the approach:

We then recorded video in b/w mode and color mode with the illuminator off and then with the illuminator on, as a subject moved from the far field to the near field. The illuminator off image served as a reference to compare the practical benefits of deploying visible white-light illumanators in a real-world surveillance application. Here is a sample preview:

Finally, we compared three (3) day/night cameras throughout a series of tests featuring both long- and mid-range illuminators, b/w mode and color mode settings, and wide, moderate and narrow FoVs). Here is an unmarked preview:

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This approach allowed us to quantitatively and systematically understand the potential benefits and tradeoffs of using white light LEDs. Inside we answer questions including:

How significant of an impact did the white light LEDs have on camera performance?

How much light did the white light LEDs add at different areas within the scene?

What, if any, decreases in bandwidth consumption did the LEDs deliver?

Which, of any, of the 3 cameras performed the best? In what conditions?

Should you even consider using white light LEDs?

Here are key findings of testing the white light LED illuminators:

The illuminators added a surprisingly significant amount of light that lit up a fairly large field, especially the long range one whose coverage was more than half of a football field.

While aiming the illuminators in line with the camera allowed maximizing the light used, it created hot spots near the camera that washed out subjects in the near field. The more powerful long-range illuminator exhibited more of this problem than the mid-range one.

Of the three D/Ns tested, the Axis P1344 tended to minimize glare and provide the most details at close range to the illuminators (even with the Bosch illuminator and against Bosch cameras.

Of the three D/Ns tested, the SD Bosch provided the most details at far range. This is likely because the SD Bosch has the best low light sensitivity and was able to product the best image with the least overall light.

When subjects were at close range to the illuminator, B/W mode tended to mitigate facial glare more effectively than did color mode

B/W or Color mode delivered relatively similar amount of details throughout the distances tested.

Bandwidth: Both illuminators reduced bandwidth for the VBR streaming camera. Relative to ambient lighting alone, the long range illuminator reduced bandwidth about 40% for both color and B&W modes. The mid range illuminator reduced bandwidth 25% in both color and B&W relative to ambient lighting alone. Do NOT take this as a universal metric. It will depend on many factors but there is a clear decrease in bandwidth consumption that we believe is caused by cameras being able to automatically reduce gain levels becaused of increased lighting.

When estimating performance benefit, estimate based on lux increase the white light LED can deliver rather at specific distances rather than the coarse grain maximum distance specified.

In light of these findings the following is recommended:

Mount long range illuminators at greater heights to create a more diffuse lighting effect for close range objects/subjects

If details are a priority, especially at close range (where illumination is ~30 lux or greater), consider using B/W mode versus Color mode to minimize glare.

Where the maximum illumination within a scene is no more than ~25 lux, consider Color mode to maximize richness (e.g. clothing and vehicle color, complexion etc.) of video information

Consider cameras with good low-light sensitivity (e.g. SD vs. 720p) over higher resolution for scenes with ~25 lux and under

Should You Use White Light LEDs?

The biggest benefit that the white light LEDs delivered over any alternatives was the additional of visible light and the potential visual deterrent inherent in lighting areas. At ~$500 to ~$1500 for the white light LEDs tested, they are not cheap compared to IR but they are a relatively simple and low cost way to add in visible lighting. For those users who prefer to capture color and/or add visible light for deterrence, white light LED are worthwhile to consider.

Physical Overview

In this video we provide a physical overview of the long-range illuminator (Bosch SLED30-WBD) and the mid-range illuminator (Iluminar WL220-60-24) used in our test. Both illuminators feature an adjustable photocell, telemetry input, U-bolt mounting bracket, power adjustment, and a pressure equalization vent. A notable difference is the size and weight of the units, with the long-range unit being quite hefty (~8 lbs.) and may require a more thoughtful mounting stategy. In contrast, the mid-range illuminator is fairly light-weight (2.3 lbs.) and can be mounted directly onto a camera housing.

Long-Range Illuminator Lux Map (Bosch SLED30-WBD)

The following diagram depicts, empirically, the additional lux the long-range illuminator delivers at various locations within the test scene. Lux measurements were obtained at both the center of the FoV where illumination was greatest, and at the fringe where illumination diminished. The white 'angle' indicates, graphically, the manufacturers stated beam-width and distance maximums.

The additional lux delivered was quite substantial - even at or past the manufacturer's rated specification for both vertical and horizontal coverage.

The following diagram depicts, empirically, the additional lux that is provided by the mid-range illuminator at various locations within the test scene. Lux measurements were obtained at both the center of the FoV where illumination was greatest, and at the fringe where illumination diminished. The white 'angle' indicates, graphically, the manufacturers stated beam-width and distance maximums.

The additional lux delivered was fairly modest with a material increase in light to about 50 - 75 feet. Beyond that, the increase in light is too low to make of a practical difference.

Long-Range Illuminator w/ B/W Mode (Center)

During this long-range illumination scenario the D/N camera is forced to B/W mode.

*In the background of the 'Illumination Off' images it might appear that there is more illumination than the measured ~0.5 lux, however it is due to a transient source of lighting that bears no material effect at the point of the subject.

The manufacturer's stated maximum illumination distance is 165ft. Examining images taken at 150ft as an approximation of the 165ft mark set by the manufacturer, reveals that the illuminator provides ~5 lux of additional lighting for a total of ~5.5 lux at the subject's location. In the 'Illumination Off' scenario the subject appears as a silhouette, with no additional details. With illumination turned on, the image provides greater contrast and, hence, potential indications and details of the subjects clothing, build, gender, and perhaps hair-style. Of course these indications/details are somewhat limited by the camera's wide FoV, and could, conversely, be enhanced if the camera is adjusted to a narrower lens angle. Indeed, with the 720p camera's current lens-angle of ~50 degrees the image provides only ~9ppf at this distance. For example if we were to match the lens angle to the manufacturer's stated beam-width of 30 degrees, ~16ppf could be obtained at this distance with a 720p camera.

At the 50ft distance (47ft HFoV), lack of lighting should not limit image quality as ~25.5 lux is provided here. Moreover, not much glare or wash-out is evident at this point. The 720p image provides ~27ppf and slight to moderate levels of facial detail.

As the subject approaches the 25ft marker lux levels are quite high at ~41.5 lux, but the drawback of a 'point' light source versus a more diffused natural light source is evident as the subject's face is obscured to a degree by glare. However, clothing and other less reflective object details have still been enhanced by additional lux and resolution (~55ppf).

Long-Range Illuminator w/ Color Mode (Center)

During this long-range illumination scenario the D/N camera is forced to color mode.

*In the background of the 'Illumination Off' images it might appear that there is more illumination than the measured ~0.5 lux, however it is due to a transient source of lighting that bears no material effect at the point of the subject.

At the 150ft mark (near the manufacturer's stated max illumination distance of 165ft), the scene with illumination is materially 'brighter' than the scene without illumination. Details are still rather limited given the wide HFoV, but the color provides better indications of clothing color and complexion versus the b/w mode images.

As the subject approaches the 50ft (HFoV ~47ft), details emerge that deliver a slight to moderate chance at identification. Note again that at the 25ft (HFoV ~23ft) mark the subject's face produces considerable glare and actually now tends to diminish details. The clarity of less reflective items, however, has still increased relative to the 50ft (HFoV ~47ft) scenario.

Long-Range Illuminator w/ B/W Mode (Fringe)

During this long-range illumination scenario the D/N camera is forced to B/W mode.

*At 200ft in the 'Illumination Off' scene, there is a light source providing an additional ~0.5 lux.

At the 150ft mark (near the manufacturer's stated max illumination distance of 165ft), there is little to no material difference in details between the illuminator 'off' and 'on' scenes. The lux level has nearly halved in comparison to the 'center' scene (from ~5.5 lux to ~3.1 lux).

At the 100ft mark is where we begin to see material benefits with illuminator on versus off. The benefit continues at every subsequent distance. Only at the nearest 25ft mark, does a reasonable chance of identification emerge, however.

One very interesting result is that the most detailed 'fringe' b/w image (25ft) is more useful than the most detailed 'center' b/w image (25ft) despite its lower lux level. The apparent reason: illumination is less direct or more diffuse and as such glare off the subject's face is less of a diminishing factor. In the next section, we'll see that in color mode this result does not hold true, due to the prevalence of glare even in the 'fringe' shot.

Long-Range Illuminator w/ Color Mode (Fringe)

During this long-range illumination scenario the D/N camera is forced to color mode.

*At 200ft in the 'Illumination Off' scene, there is a light source providing an additional ~0.5 lux.

At the 150ft mark (near the manufacturer's stated max illumination distance of 165ft), there is little to no material difference in details between the illuminator 'off' and 'on' scenes. The lux level has nearly halved in comparison to the 'center' scene (from ~5.5 lux to ~3.1 lux).

At the 100ft mark is where we begin to see material benefits with illuminator on versus off. The benefit continues at every subsequent distance. Arguably, the most useful image results at the 50ft (HFoV ~47ft) distance, as opposed to the 25ft (HFoV ~23ft) distance, due to the excessive glare off the subject's face at the nearest marker. Note that in b/w mode the image did not feature a problematic level of glare at this distance, and was the most useful overall.

Mid-Range Illuminator w/ B/W Mode (Center)

During this mid-range illumination scenario the D/N camera is forced to B/W mode.

*In the background of the 'Illumination Off' images it might appear that there is more illumination than the measured ~0.5 lux, however it is due to a transient source of lighting that bears no material effect at the point of the subject.

At the 75ft mark (near the manufacturer's stated max illumination distance of 82ft), there is a slight material benefit in details between the illuminator 'off' and 'on' scenes. The illuminator adds only ~1.7 lux at this distance but manages to produce a modicum of benefit as gross body contours, and contrast in clothing and complexion are revealed.

Picture quality continues to increase relative to the 'off' images at each progressive marker inwards. However, it is not until the nearest 25ft (HFoV ~23ft) mark that a reasonable chance at identification is obtained. Unlike the analogous scene under the long-range illuminator, the mid-range product does not engender a deleterious glare off the subject's face.

Mid-Range Illuminator w/ Color Mode (Center)

During this mid-range illumination scenario the D/N camera is forced to B/W mode.

*In the background of the 'Illumination Off' images it might appear that there is more illumination than the measured ~0.5 lux, however it is due to a transient source of lighting that bears no material effect at the point of the subject.

Results are overall quite similar to the analogous b/w mode scenes. In this color mode test, a slight material benefit provided by the illuminator is observed at the 75ft (HFoV ~70ft) distance (near the manufacturer's stated max illumination distance of 82ft).

Picture quality continues to increase relative to the 'off' images at each progressive marker inwards. However, it is not until the nearest 25ft (HFoV ~23ft) mark that a reasonable chance at identification is obtained. Unlike the analogous scene under the long-range illuminator, the mid-range product does not engender a deleterious glare off the subject's face.

Mid-Range Illuminator w/ B/W Mode (Fringe)

During this mid-range illumination scenario the D/N camera is forced to B/W mode.

*At 200ft in the 'Illumination Off' scene, there is a light source providing an additional ~0.5 lux.

At the 75ft mark (near the manufacturer's stated max illumination distance of 82ft), there is a very slight advantage in details between the illuminator 'off' and 'on' scenes. In the 'off' image the subjects arms cannot be distinguished from the torso, and may lead an investigator to conclude the subject is heavier set. The 'on' image clearly shows a delineation between the two body structures and represents the build and perhaps gender more accurately. The lux level drops from 2.2 lux at center to 1.4 lux here at fringe.

At the 50ft mark we see stronger material benefits with illuminator on versus off, where there are now better indications of the subject's build, and gender. As in the analogous 'center' test, reasonable odds of identification are not observed until the final 25ft (HFoV ~23ft) mark. The analogous 'center' image provides only a modicum of additional clarity with nearly twice the lux (14.5 lux versus 7.5 lux).

Mid-Range Illuminator w/ Color Mode (Fringe)

During this mid-range illumination scenario the D/N camera is forced to color mode.

*At 200ft in the 'Illumination Off' scene, there is a light source providing an additional ~0.5 lux.

At the 75ft mark (near the manufacturer's stated max illumination distance of 82ft), there is a slight advantage provided by the illuminator. In the 'off' image the subject body blends in with the shadowy background. Whereas, with the illuminator on the subject clearly stands out from the background. Indications of build and gender are afforded as well. The lux level drops from 2.2 lux at center to 1.4 lux here at fringe.

At the 50ft mark we see fairly strong material benefits with illuminator on versus off, where there are now clearer indications of the subject's build, gender, and complexion. As in the analogous 'center' test, reasonable odds of identification are not observed until the final 25ft (HFoV ~23ft) mark. The analogous 'center' image provides a fair degree of additional clarity with nearly twice the lux (14.5 lux versus 7.5 lux). As such, the difference between center and fringe is slightly more pronounced in color than in b/w.

Camera Comparison under Long-Range Illuminator (Wide FoV)

The following compares three (3) D/N cameras under the long-range illuminator at a wide FoV of ~93ft. The light level is measured at ~10.5 lux. In the first composite, D/Ns are forced to B/W mode, while in the second composite D/Ns are forced to color mode. The subject is positioned at center of FoV where illumination is greatest.

Details are expectedly weak across the board in this wide FoV. Among the field however, the P1344 appears to provide the crispest picture. The NBN-921 exhibits quite a bit of compression artifacts, while the NBN-498 appears overly bright or wash-out to a degree.

Again the same general results as in the b/w version of this composite. In comparing the b/w to this color mode, however, it can be argued that color offers more utility due to the added richness of color information (e.g. clothing color and complexion etc.)

Camera Comparison under Long-Range Illuminator (Moderate FoV)

The following compares three (3) D/N cameras under the long-range illuminator at a moderate FoV of ~47ft. The light level is measured at ~25.5 lux. In the first composite, D/Ns are forced to B/W mode, while in the second composite D/Ns are forced to color mode. The subject is positioned at center of FoV where illumination is greatest.

In both the NBN-921 and NBN-498 the subject's face is obscured by glare. The P1344, thus, provides the best level of detail among the field. As in the previous wide FoV, the NBN-921 exhibits compression artifacts and the NBN-498 appears slightly over-exposed.

Essentially the same results as in the previous b/w mode composite. The P1344 provides greatest facial detail among the field, as the other two images exhibit glare on the subject's face.

Camera Comparison under Long-Range Illuminator (Narrow FoV)

The following compares three (3) D/N cameras under the long-range illuminator at a narrow FoV of ~23ft. The light level is measured at ~41.5 lux. In the first composite, D/Ns are forced to B/W mode, while in the second composite D/Ns are forced to color mode. The subject is positioned at center of FoV where illumination is greatest.

At this narrow field of view with ~41.5 lux, we might expect good odds of subject identification across the board. However, this is not the case as point source lighting produces considerable glare on the subject's face, across all cameras. The effect is least deleterious in the P1344, making its image here the most useful.

Same key results seen here in color as were observed in the previous b/w scenario. Across the board glare is quite severe and obscures subject facial details considerably. Overall the P1344 appears to mitigate these effects the best, and provides the most useful image.

Camera Comparison under Mid-Range Illumination (Wide FoV)

The following compares three (3) D/N cameras under the mid-range illuminator at a wide FoV of ~93ft. The light level is measured at ~2.2 lux. In the first composite, D/Ns are forced to B/W mode, while in the second composite D/Ns are forced to color mode. The subject is positioned at center of FoV where illumination is greatest.

Note that this distance of 100ft is beyond the manufacturer's stated max distance of 82ft. At this very low lux level of 1.5 low-light sensitivity may be the distinguishing factor between camera performance. Indeed, the SD NBN-498 provides the most useful image as a subject is detectable. A modicum of details are provided as well such as gross body contours which may indicate build and gender. The P1344 is quite dark and the subject is barely detectable. The 720p NBN-921 is simply useless with no discernible subject within the image.

Switching to color mode at this distance and light level does not change the cardinal order of usefulness between the cameras, but it does provide the P1344 slight improvement. Evidently, color seems to improve the contrast between subject and background in the case of the P1344. The SD provides the most detail, but the orientation of the subject is not as clear as it was in b/w mode. The subject almost appears to be facing obliquely to the cameras when in fact the subject is facing head-on.

Camera Comparison under Mid-Range Illuminator (Moderate FoV)

The following compares three (3) D/N cameras under the mid-range illuminator at a moderate FoV of ~47ft. The light level is measured at ~4.3 lux. In the first composite, D/Ns are forced to B/W mode, while in the second composite D/Ns are forced to color mode. The subject is positioned at center of FoV where illumination is greatest.

The subject, now at 50ft, is well within the manufacturer's stated max distance of 82ft. The lux level is fairly low at 4.3, and the SD NBN-498 tends to yield the better results compared to the two 720p D/Ns. Indeed noise and pixelation obscures details significantly in both the 720p NBN-921 and 720p P1344. For example, in the P1344 image the subject could conceivably be mistaken to have a side-part hair-style, when in fact the subject has a shaved head - as more clearly depicted in the SD NBN-498.

The color mode images provide an advantage in assessment of details related to color information (e.g. clothing and complexion), but there is a clear loss of picture clarity due to increased noise and pixelation. This is most evident in the two 720p cameras (P1344 and NBN-921). For the SD NBN-498 noise, pixelation and subsequent loss of picture clarity is not materially an issue going from b/w to color.

Camera Comparison under Mid-Range Illuminator (Narrow FoV)

The following compares three (3) D/N cameras under the mid-range illuminator at a narrow FoV of ~23ft. The light level is measured at ~14.5 lux. In the first composite, D/Ns are forced to B/W mode, while in the second composite D/Ns are forced to color mode. The subject is positioned at center of FoV where illumination is greatest.

Somewhat unexpectedly, the 720p P1344 and SD NBN-498 image qualities are nearly on par at this narrow FoV and moderately high light level (~14.5 lux). Perhaps a slight edge in crispness does go to the 720p P1344. Also, quite surprisingly, the other 720p, the NBN-921, actually does worse than its SD counterpart, the NBN-498.

Across the board, the color mode images in this composite provide more detail than their b/w mode counterparts. Given detail levels, all cameras provide at least moderate odds of identification. In terms of facial details the P1344 and NBN-498 are fairly even, but the P1344 exhibits an edge in color fidelity.

Methodology

Illuminators

Illuminators were mounted ~15 AGL (at the same height as the cameras).

Here are the illuminators with their key manufacturer stated specifications:

All D/Ns were normalized to a maximum exposure of 1/30s and fixed to either monochrome or color mode depending on the scene. All camera lens angles were adjusted to ~50 degrees to provide a uniform HFoV in which to make image quality comparisons.

In all eight (8) scenarios markers were positioned at roughly 200ft, 150ft, 100ft, 75ft, 50ft and 25ft distances from the camera/illuminator setup. With the camera lens angle at ~50 degrees these distances correspond to HFoVs of roughly 187ft, 140ft, 93ft, 70ft, 47ft, and 23ft, respectively. The subject begins at the 200ft mark and progressively walks inwards, momentarily pausing at each marker until finally reaching the last marker at 25ft.

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The world's leading video surveillance information source, IPVM provides the best reporting, testing and training for 10,000+ members globally. Dedicated to independent and objective information, we uniquely refuse any and all advertisements, sponsorship and consulting from manufacturers.